Sihombing, S., and D. Sitanggang. “ANALISIS DESAIN PRODUK DAN JASA”. Jurnal Riset Akuntansi &Amp; Keuangan, vol. 4, no. 2, June 2019, pp. 137-56, https://ejournal.ust.ac.id/index.php/JRAK/article/view/456.